There are three main challenges that need to be addressed by a so-called 5G wireless communication system to enable a truly “networked society,” where information can be accessed and data shared anywhere and anytime, by anyone and anything. These are:                massive growth in the number of connected devices.        A massive growth in traffic volume.        An increasingly wide range of applications with varying requirements and characteristics.        
To handle massive growth in traffic volume, wider frequency bands, new spectrum, and in some scenarios denser deployment are needed. Most of the traffic growth is expected to be indoor and thus indoor coverage is important.
New spectrum for 5G is expected to be available after 2020. The actual frequency bands, and the amount of spectrum, have not yet been identified. The identification of frequency bands above 6 GHz for mobile telecommunications will be handled in the World Radio Conference in 2019 (WRC-19). New frequency bands below 6 GHz for mobile telecommunications are handled in WRC-15. Eventually, all mobile telecommunications bands, from below 1 GHz, up to as high as 100 GHz, could potentially become candidates for 5G. However, it is expected that the first commercial deployment of 5G will happen in frequency bands close to 4 GHz, and that 28 GHz deployments will come later.
The International Telecommunication Union (ITU) has outlined a vision for 5G, which it will refer to as “IMT-2020,” providing a first glimpse of potential scenarios, use cases and related ITU requirements that eventually will define 5G.
The 3rd-generation Partnership Project (3GPP) has begun its journey towards 5G, with a 5G workshop held in September 2015. A study item on channel modelling for spectrum above 6 GHz has been approved. Development of specifications for 5G in 3GPP is likely to be split across multiple releases, with two phases of normative work. Phase 1 is expected to be completed in the second half of 2018. It will fulfil a subset of the complete set of requirements and target the need for early commercial deployments in 2020 expressed by some operators. Phase 2, targeted for completion by the end of 2019, will meet all identified requirements and use cases.